I have a bunch of contact data listing what members were contacted by what offer, which summarizes something like this:
To make sense of it (and to make it more scalable) I was considering creating dummy variables for each offer and then using a logistic model to see how different offers impact performance:
Before I embark too far on this journey I wanted to get some input if this is a sensible way to approach this (I have started playing around but and got a model output, but haven't dug into it yet). Someone suggested I use linear regression instead, but I'm not really sure about the approach for that in this case.
What I'm hoping to get are coefficients that are interpretable - so I can see that Mailing the 50% off offer in the 3d mailing is not as impactful as the $25 giftcard etc, and then do this at scale (lots of mailings with lots of different offers) to draw some conclusions about the impact of timing of different offers.
My concern is that I will end up with a fairly sparse matrix where only some combinations of the many possible are respresented, and what problems may arise from this. I've taken some online courses in ML but am new to it, and this is one of my first chances to work directly with it so I'm hoping I could create something useful out of this. I have access to lots and lots of data, it's just a matter of getting something basic out that can show some value. Maybe there's already some work on this or even some kind of library I can use?
Thanks for any help!
If your target variable is binary (1 or 0) as in the second chart, then a classification model is appropriate. Logistic Regression is a good first option, you could also a tree-based model like a decision tree classifier or a random forest.
Creating dummy variables is a good move; you could also convert the discounts to numerical values if you want to keep them in a single column, however this may not work so well for a linear model like logistic regression as the correlation will probably not be linear.
If you wanted to model the first chart directly you could use a linear regressions for predicting the conversion rate, I'm not sure about the difference is in doing this, it's actually something I've been wondering about for a while, you've motivated me to post a question on stats.stackexchange.com
Related
I am very new to data science, so I have a (basic?) question:
I have a set of materials (let's say plastics, glass, concrete…). I have a bunch of characteristics of each material (e.g. toughness, translucency) and for each of these materials I also have a score how they perform in a certain test.
Now I want to find out if there is some kind of correlation between the characteristics and the performance score. There is no linear correlation, I assume that it some combination of some (but not all) of the characteristics.
How do I go about finding out how they are "connected" ? What are the best methods? I was thinking of training a neural network but I don't have that much data and also, it seems like a bit of an overkill.
As I said I am very new to this so I am grateful for any hint or term I need to search for (I work with Python, btw).
To find correlation between characteristics of your materials and their performance in a certain test,you can try to use machine learning algorithms like a decision tree or a random forest. its simple to use with even less data.
you need to experiments different algorithms to find best approach that works for you.
I am using lifelines package to do Cox Regression. After trying to fit the model, I checked the CPH assumptions for any possible violations and it returned some problematic variables, along with the suggested solutions.
One of the solution that I would like to try is the one suggested here:
https://lifelines.readthedocs.io/en/latest/jupyter_notebooks/Proportional%20hazard%20assumption.html#Introduce-time-varying-covariates
However, the example written here is using CoxTimeVaryingFitter which, unlike CoxPHFitter, does not have concordance score, which will help me gauge the model performance. Additionally, CoxTimeVaryingFitter does not have check assumption feature. Does this mean that by putting it into episodic format, all the assumptions are automatically satisfied?
Alternatively, after reading a SAS textbook on survival analysis, it seemed like their solution is to create the interaction term directly (multiplying the problematic variable with the survival time) without changing the format to episodic format (as shown in the link). This way, I was hoping to just keep using CoxPHFitter due to its model scoring capability.
However, after doing this alternative, when I call check_assumptions again on the model with the time-interaction variable, the CPH assumption on the time-interaction variable is violated.
Now I am torn between:
Using CoxTimeVaryingFitter without knowing what the model performance is (seems like a bad idea)
Using CoxPHFitter, but the assumption is violated on the time-interaction variable (which inherently does not seem to fix the problem)
Any help regarding to solve this confusion is greatly appreciated
Here is one suggestion:
If you choose the CoxTimeVaryingFitter, then you need to somehow evaluate the quality of your model. Here is one way. Use the regression coefficients B and write down your model. I'll write it as S(t;x;B), where S is an estimator of the survival, t is the time, and x is a vector of covariates (age, wage, education, etc.). Now, for every individual i, you have a vector of covariates x_i. Thus, you have the survival function for each individual. Consequently, you can predict which individual will 'fail' first, which 'second', and so on. This produces a (predicted) ranking of survival. However, you know the real ranking of survival since you know the failure times or times-to-event. Now, quantify how many pairs (predicted survival, true survival) share the same ranking. In essence, you would be estimating the concordance.
If you opt to use CoxPHFitter, I don't think it was meant to be used with time-varying covariates. Instead, you could use two other approaches. One is to stratify your variable, i.e., cph.fit(dataframe, time_column, event_column, strata=['your variable to stratify']). The downside is that you no longer obtain a hazard ratio for that variable. The other approach is to use splines. Both of these methods are explained in here.
I want to build a model that describes a curve that fits the data shown in the scatterplot. I thought it would be straight forward using sklearn. But the choice and application of the different methods gets rather confusing.
Which algorithms would you use to tackle this problem?
This is really a question for CrossValidated rather than a Python question.
Your data seems to strongly indicate a simple underlying model which is linear until the very end, when it perhaps becomes polynomial.
As a first step, if possible, I would investigate this phenomenon. It's unusual. Perhaps there's something wrong with the data source. But maybe not. For example, a physical phenomenon with two distinct phases might produce data like these.
As to models, I would suggest natural cubic splines for this data. They are simple and involve cutting the data up into windows which you fit with cubic polynomials (a special case of which is a line).
You might also consider smoothing splines, and local regression.
For information on these, see the free online textbook, An Introduction to Statistical Learning.
I'm working on a model that would predict an exam schedule for a given course and term. My input would be the term and the course name, and the output would be the date. I'm currently done with the data cleaning and preprocessing step, however, I can't wrap my head around a way to make a model whose input is two strings and the output is two numbers (the day and month of exam). One approach that I thought of would be encoding my course names, and writing the term as a binary list. I.E input: encoded(course), [0,0,1] output: day, month. and then feeding to a regression model.
I hope someone who's more experienced could tell me a better approach.
Before I start answering your question:
/rant
I know this sounds dumb and doesn't really help your question, but why are you using Neural Networks for this?!
To me, this seems like the classical case of "everybody uses ML/AI in their area, so now I have to, too!" (which is completely not true) /rant over
For string-like inputs, there exist several methods to encode these; choosing the right one might depend on your specific task. As you have a very "simple" (and predictable) input - i.e., you know in advance that there might not be any new/unseen course titles during testing/inference, or you do not need contextual/semantic information, you can resort to something like scikit-learn's LabelEncoder, which will turn it into different classes.
Alternatively, you could also throw a more heavy-weight encoding structure at the problem, that embeds the values in a matrix. Most DL frameworks offer some form of internal function for this, which basically requires you to pass an unique index for your input data, and actively learns some k-dimensional embedding vector for this. Intuitively, these embeddings correspond to a semantic or topical direction. If you have for example 3-dimensional embeddings, the first one could represent "social sciences course", the other one "technical courses", and the third for "seminar".
Of course, this is just a simplification of it, but helps imagining how it works.
For the output, predicting a specific date is actually a really good question. As I have personally never predicted dates myself, I can only recommend tips by other users. A nice answer on dates (as input) is given here.
If you can sacrifice a little bit of accuracy in the result, predicting the calendar week in which the exam is happening might be a good idea. Otherwise, you could simply treat it as two regressed values, but you might end up with invalid combinations (i.e. "negative days/months", or something like "31st February".
Depending on how much training data of high quality you have, results might vary quite heavily. Lastly, I would again recommend you to overthink whether you actually need a neural network for this task, or whether there are simpler metrics to do this.
Create dummy variables or use RandomForest. They accept text input and numerical output.
My Question is as follows:
I know a little bit about ML in Python (using NLTK), and it works ok so far. I can get predictions given certain features. But I want to know, is there a way, to display the best features to achieve a label? I mean the direct opposite of what I've been doing so far (put in all circumstances, and get a label for that)
I try to make my question clear via an example:
Let's say I have a database with Soccer games.
The Labels are e.g. 'Win', 'Loss', 'Draw'.
The Features are e.g. 'Windspeed', 'Rain or not', 'Daytime', 'Fouls committed' etc.
Now I want to know: Under which circumstances will a Team achieve a Win, Loss or Draw? Basically I want to get back something like this:
Best conditions for Win: Windspeed=0, No Rain, Afternoon, Fouls=0 etc
Best conditions for Loss: ...
Is there a way to achieve this?
My paint skills aren't the best!
All I know is theory, so well you'll have to look for the code..
If you have only 1 case(The best for "x" situations) the diagram becomes something like (It won't be 2-D, but something like this):
Green (Win), Orange(Draw), Red(Lose)
Now if you want to predict whether the team wins, loses or draws, you have (at least) 2 models to classify:
Linear Regression, the separator is the Perpendicular bisector of the line joining the 2 points:
K-nearest-neighbours: it is done just by calculating the distance from all the points, and classifying the point as the same as the closest..
So, for example, if you have a new data, and have to classify it, here's how:
We have a new point, with certain attributes..
We classify it by seeing/calculating which side of the line the point comes in (or seeing how far it is from our benchmark situations...
Note: You will have to give some weightage to each factor, for more accuracy..
You could compute the representativeness of each feature to separate the classes via feature weighting. The most common method for feature selection (and therefore feature weighting) in Text Classification is chi^2. This measure will tell you which features are better. Based on this information you can analyse the specific values that are best for every case. I hope this helps.
Regards,
Not sure if you have to do this in python, but if not, I would suggest Weka. If you're unfamiliar with it, here's a link to a set of tutorials: https://www.youtube.com/watch?v=gd5HwYYOz2U
Basically, you'd just need to write a program to extract your features and labels and then output a .arff file. Once you've generated a .arff file, you can feed this to Weka and run myriad different classifiers on it to figure out what model best fits your data. If necessary, you can then program this model to operate on your data. Weka has plenty of ways to analyze your results and to graphically display said results. It's truly amazing.